- A
- B
- C
- D
Step-by-Step Solution
Read the divisors down the ladder: 252 ÷ 2 = 126, ÷ 2 = 63, ÷ 3 = 21, ÷ 3 = 7, ÷ 7 = 1. So . (21, 4 and 9 are not prime; , not 252.)
Answer: C)
Rohan finds the prime factors of 252 by repeated division on a ladder. Two divisors are hidden by ?. Which is the complete prime factorisation of 252?
Class 6Playing with NumbersPlaying with Numbers
Key idea: Prime vs composite
A whole number greater than 1 is **prime** if it has exactly two factors: 1 and itself. It is **composite** if it has more than two factors. The number 1 is neither prime nor composite (it has only one factor — itself). 2 is the only **even** prime; every other even number is divisible by 2 and so has at least three factors.
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